Facebook can tell us who is dating who, who checked in where — and now, who has an STD? As reported by Salon, researchers are now viewing social networking sites like Facebook as potential tools for predicting and preventing STD transmission.

One of these researchers, Peter Leone, a professor of medicine at the University of North Carolina’s Center for Infectious Diseases, concludes that the risk of contracting HIV extends to immediate friend circles, and not just sexual partners. He reasons that people in the same social circle often behave in similar risk-taking patterns and sleep with the same people — giving the term mutual friends a whole new meaning.

Leone cites an outbreak of syphilis in North Carolina as an example. After asking patients who they hung out with, he was able to connect 80% of the cases. Going off this, Leone then asked patients recently diagnosed with HIV for a list of friends they think are mostly likely to be at risk. With the patient’s permission, they notify people that someone they know has been diagnosed with HIV and they may be at risk as well. Not exactly your everyday Facebook message.

This strategy is a whole new way of thinking about STD transmission; it doesn’t just target the usual, at-risk demographics. Using Facebook enables people like Leone to make connections that may not be obvious at first.

However, a hypothetical STD app that acts in a similar fashion poses privacy risks. What happens if the news of someone’s STD diagnosis splashes up on everyone’s news feed? The stigma associated with STDs may deter people from using the app in the first place. But researchers like Leone view Facebook as a way to combat this stigma through tactics such as posting status updates about getting tested and checking in on Foursquare when in the clinic.